In recent years, in a lithographic process to produce a semiconductor, a liquid crystal display device or the like, due to higher integration of semiconductors or the like, the sequentially moving type exposure apparatus is mainly used, such as the reduction projection exposure apparatus based on a step-and-repeat method (the so-called stepper) that can form a fine pattern on a photosensitive object with good accuracy and high throughput, the scanning projection exposure apparatus based on a step-and-scan method (the so-called scanning stepper (also called a scanner)) or the like.
In these types of exposure apparatus, as a drive unit for driving a photosensitive object such as a wafer or a glass plate (hereinafter referred to as a “wafer”), a wafer stage unit of a coarse/fine movement structure has been used, which has an XY stage supported by levitation by air bearings or the like on a platform and is driven within a two-dimensional plane by a two-axis linear motor, and a wafer table that holds a wafer on the XY stage and is finely driven in a Z-axis direction and a direction of inclination by voice coil motors or the like. Further, a wafer stage unit that is equipped with a single stage driven in directions of six degrees of freedom by linear motors or voice coil motors is also recently being developed.
However, in the wafer stage units referred to above, because wiring used in the linear motors or voice coil motors, piping (tubes) used in the air bearings or the like connects from the outside to the stage, the wiring, piping or the like was dragged along with the drive of the stage, which caused a decrease in position controllability of the wafer.
In order to improve such an inconvenience, for example, a moving magnet type linear motor can be used for driving the stage and pressurized gas for supporting the stage on the platform by levitation can also be supplied from the platform side, which allows the wiring, piping or the like connecting to the stage to be removed (for example, refer to Patent Document 1).
However, although it is relatively easy to employ the structure according to Patent Document 1 in which pressurized gas is supplied from the platform side to the stage side in a stage which is scanned in an uniaxial direction (e.g. scanning direction) such as in a reticle stage in the scanner, it is difficult to employ the structure in a wafer stage to which two-dimensional movement is essential. Therefore, in a wafer stage unit, the piping for supplying pressurized gas had to be connected to the stage, which left the piping dragging and still being a cause in the decrease in position controllability of the stage. As a matter of course, in the case piping inevitably has to be connected to the reticle stage also in a reticle stage unit, there is a similar risk of a decrease in position controllability.    Patent Document 1: Kokai (Japanese Unexamined Patent Application Publication) No. 2001-20951